A fitting system of this type is known from DE 20 2010 015 171 U1. Actuation of the hand lever causes rotation of the transmission rod which, in turn, unlocks the two fittings counter to the force of the spring arrangements contained therein. The torque characteristic of the spring arrangements serving to secure the locked state runs linearly, i.e. the torque opposed to the unlocking operation rises sharply during the unlocking operation as the angle of rotation increases. In order to increase the ease of operation, a flatter profile would be advantageous. For example, it is proposed in DE 196 33 782 C1 to use a helical buckling spring for securing the locked state of the fitting system. The characteristic of said spring runs virtually independently of the unlocking path, and therefore the force which is opposed to the unlocking operation and is to be overcome by the user remains virtually constant. In DE 100 38 778 B4, the user is assisted during the unlocking operation by a toggle lever which improves the expenditure of force.